Apparatus for shrinking a wrapping around a transport unit by means of radiant energy

ABSTRACT

In an apparatus for shrinking wrappings of heat-shrinkable sheet plastic surrounding transport units by subjecting the wrapped units to directional radiant energy from emitters, the emitters are turnably and movably mounted and actuated to more or less accurately follow the contour of said unit at some distance therefrom so as to irradiate all portions of the unit wrapping more uniformly.

United States Patent [1 1 Gustavsson 1 APPARATUS FOR SHRINKING A WRAPPING AROUND A TRANSPORT UNIT BY MEANS OF RADIANT ENERGY [76] Inventor: Olov Erland Gustavsson,

lndustrivagen 10, Kungalv, Sweden 22 Filed: Aug. 28, 1972 21 Appl. No.: 283,997

[30] Foreign Application Priority Data Sept. 9, 1971 Sweden 11430/71 [52] US. Cl 425/174.4, 425/383, 219/388, 219/354, 53/184, 118/620 [51] Int. Cl....; 1329f 5/00- [58] Field of Search 425/384, 174.4, 174, 174.2; 53/184, 30; 219/388; 118/641, 642, 643; 156/380, 499, 85, 86; 432/18, 59; 34/41,

[56] v 7 References Cited I UNITED STATES PATENTS 3,710,550

1/1'973 Osborne 53/184 [n 3,801,246 Apr. 2, 1974 3,196,888 7/1965 Rousseau 134/180 X 2,387,516 10/1945 Kaminskim; 3,557,808 l/197l Ctusse 134/45 Primary Examiner-J. Spencer Overholser Assistant Examiner-David B. Smith Attorney, Agent, or FirmFred Philpitt [57] ABSTRACT In an apparatus for shrinking wrappings of heatshrinkable sheet plastic surrounding transport units by subjecting the wrapped units to directional radiant energy from emitters, the emitters are turnably and movably mounted and actuated to more or less accurately follow the contour of said unit at some distance therefrom so as to irradiate all portions of the unit wrapping more unifonnly.

12 Claims, 5 Drawing Figures PATENTEU APR 2 1974 3,801,246 'SHEEI 1 [IF 2 MENTEUAPR 2 I574 SHEET 2 [1P2 lL llL- APPARATUS FOR SHRINKING A WRAPPING AROUND A TRANSPORT UNIT BY MEANS OF RADIANT ENERGY The present invention relates to an apparatus for shrinking a wrapping of heat-shrinkable sheet plastic that surrounds a transport unit, for example a pile of goods, by subjecting said wrapping to radiant energy emitted from at least one emitter unit adapted for directional irradiation, and comprising means for effecting a relative movement between the wrapped transport unit and the emitter unit in a predetermined direction, the emitter unit being arranged to irradiate successive surface portions or-zones of the shrinkable wrapping of the transport unit during successive stages of said relative movement.

It is previously known to shrink a wrapping of heatshrinkable sheet plastic surrounding a transport unit by subjecting said wrapping to radiant energy from one or more emitter units of a directional type. This offers many important advantages in comparison with the previously common blowing out of hot air towards the wrapping on the transport unit. For the first the radiant energy, the character and wavelength of which can be varied within rather wide limits only it brings about the required heating of the sheet plastic wrapping, is effective from a considerably greater distance than is hot air blown out through nozzle holes or apertures, which means that it is not so critical to locate the emitters very close to the passing transport unit. For the second it is much easier to direct the radiant heat so that losses to the surrounding can be considerably reduced; Furthermore the need for special means for heating the air before it is blown out is completely eliminated, which means a simplification of the apparatus.

However, in old apparatus making use of radiant energy for shrinking, the transport unit was moved relative to the radiator unit, or the latter relative to the transport unit, along a fixed and straight path only, whereby a satisfactory shrinking effect was obtained only at those sides of the transport units which were extending in the main direction of the relative movement. Although suggestions were made that the the emitter units could be directed obliquely in order to more effectively irradiate also an end surface of the transport unit, the results of such measures were never entirely satisfactory.

The object of the present invention is to provide an apparatus of the kind referred to hereinbefore, in which the emitter unit or units are capable of effectively irradiating not only those sides of the transport unit which are parallel with the main direction of the relative movement, but also the front and rear sides or end surfaces thereof as seen in the direction of movement. For the solution of this problem the invention is based on the idea that the emitter unit or units have to be made movable in such a manner that the directional radiant energy emitted therefrom will be more or less automatically directed towards different sides or surfaces of the transport unit as the position of the transport unit in relation to the emitter unit or units is changed during their relative movement.

Inits primary form the apparatus according to the present invention is characterized in that the emitter unit is turnable about at least one pivot axis that is at least approximately at right angles to the direction of the relative movement, and that the emitter unit is arranged tobe turned about said axis in response to the change in mutual position occuring between the transport unit and the emitter unit during said relative movement. In such an apparatus the emitter unit preferably has, in a manner known per se, an elongate shape, the longitudinal direction of which is at least approximately parallel with the pivot axis.

In a preferred embodiment of the invention, the emitter unit is turnable from a'first position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the front side of the transport unit as calculated in the direction of relative movement, via a second position, in which its radiant energy is hitting the wrapping of the transport unit in a direction that is substantially normal to the direction of relative movement, and into a third position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the rear side of the transport unit as calculated in the direction of relative movement, whereupon the emitter unit is returnable to said first position for treating the wrapping of a next transport unit. In this case each emitter unit is suitably turnable against the action of spring means tending to return the same to a predetermined initial position. I In a particularly advantageous form of the apparatus according to the invention, each emitter unit is tumable about two spaced but mutually parallel pivot axes, those axes suitably being spaced in the direction of said relative movement. In such a case the one pivot axis may substantially coincide with a centre axis of the emitter unit. The turning of the emitter unit may be accomplished by the aid of actuating means connected thereto and comprising wheels or arms, which directly engage with the transport unit proper during the relative movement,but it is also possible to place the transport unit on a carrier which in its turn actuates and changes the position and direction of the emitter unit or units.

For further elucidation of the invention a partially diagrammatically illustrated embodiment thereof, which is not to be considered as restrictive for the application of the inventive idea, will be described in the following and with reference to the accompanying drawings. In the drawings FIG. 1 shows an apparatus according to the invention for shrinking a sheet plastic wrapping surrounding a transport unit that is assumed to consist of a collection of goods piled on a loading pallet, the apparatus being seen from above and with its components in those positions which they occupy approximately at the very moment when the emitter units of the apparatus are energized to start emitting radiant energy during a subsequent cycle of operation.

FIG. 2 illustrates in a partially simplified manner the apparatus still seen from above but with its components in those positions which they occupy when the transport unit has been moved closer up to the emitter units and started to cause said units to perform an outwardly swinging movement.

FIG. 3 illustrates in a similar manner a still further and later stage in the shrinking operation, in which the emitter units pass along the longitudinal sides of the transport unit in order to successively shrink the sheet plastic wrapping thereon.

FIG. 4 illustrates in the same simplified manner as FIGS. 2 and 3, how the emitter units at the end of the shrinking operation are brought to irradiate the rear side of the transport unit.

FIG. finally shows a side view of the apparatus with a related belt conceyor as well as the transport unit indicated by dash-and-dot lines.

In the drawing (FIGS. 1 and 5)1designates a stand or frame structure included in the apparatus and straddling a belt conveyor 2 which is only diagrammatically indicated in FIG. 5. Resting on the conveyor 2, the running speed of which is variable or the movement of which can at least be stopped when required, transport units 3 are advanced through the stand 1 in succession but with certain interspaces'. In the drawing merely one such transport unit is shown and although this one is only diagrammatically illustrated it may be assumed that it consists of a loading pallet 4 on which rests a pile 5 of arbitrary goods, said pile being surrounded by a wrapping 60f sheet plastic being shrinkable by heating. The large arrow on the transport unit 3 in FIGS. 1-4 indicates the direction of movement thereof through the apparatus. I

On each side of the path followed by the transport unit 3 through the apparatus there is pivoted in the stand '1 a gate-like frame structure 7 that isswingable relative to the stand about a vertical axis 8 against the action of a spring 9 tending to keep the gate-like frame structure 7 in a predetermined initial position defined by an abutment 10. The arrangement including the two gate-like frame structures 7 is entirely symmetrical and each frame structure carries, at its outer, free end or marginal an emitter unit 11 which is-of elongate shape in the vertical direction. The emitter unit is in its turn rotatable-relative to the frame structure 7 about a vertical axis 12 which substantially coincides with a centre axis through the emitter unit and is defined by pivot pins at the upper and lower ends of the same. The lower one of those latterpivot pins is extended and serves as apin shaft for a freely rotatable, horizontally orientated wheel 13.

As can be seen from FIGS. l-4 the wheel 13 at each one of the symmetrically arranged, gate-like frame structures 7 is actuated by the transport unit 3, and

more specifically by'the loading pallet 4, when the transport unit is passing by, and this in such a manner that the gate-like frame structures 7 are then forced to swing outwardly and away from each other. This, of course, requires that the wheels 13 must have a diameter that is accomodated to the size and shape of the transport unit or, more specifically, of the loading pallet. Obviously the emitter units 11 will partake in the swinging movement of the gate-like frame structures 7 about the vertical axes 8 but their aiming relative to the respective frame structure is not changed so far. To

' each emitter unit 11 there is rigidly connected an actuating arm 14 which with its free, suitably ball-shaped end projects a small distance beyond the circumference of the relatedwheel 13 and which is also adapted to be actuated by the passing transport unit 3 or, in the case illustrated, by the loading pallet 4.

As can be readily understood from FIGS. l-4 the transport unit during its passage through the apparatus firstly causes the gate-like frame structures 7 to swing outwards from each other by actuating the wheels 13. Then, when the foremost end of the transport unit has reached a position approximately at a crossing plane through the pivot axes 12 of the two emitter units 11, it will also actuate the arms 14 and thus bring about a r 4 v step-wise turning of the emitter units relative to the frame structure. The initial position of the arms 14 and thus of the emitter units 11 according to FIGS. 1 and 2 are determined by the one side of abutments l5, and the emitter units together with the arms 14 tend to return to this initial position under the actuation of spring means, not shown.

The abutment 15 for each emitter unit 11 is mounted on an arm 16 that is attached to the related gate-like frame structure 7 and has at its outer end an electromagnetically releasable pawl 17. This pawl is adapted to engage and retain a projection 18 on the emitter unit 1 1 when the latter has been turned approximately 270 about the axis 12 and, hence, has come into contact with the opposite side of the abutment 15. This occurs when the transport unit 4 has just passed the wheelsl3 in accordance with what has been shown by dash-anddot lines in FIG. 4, at which occasion the springs 9 positively return the gate-like frame structures 7 to their initial positions against the abutments l0, i.e. swing said structures inwardly and towards one another. It follows from this that the springs 9 must be strong enough to overcome the spring means, not shown, which tend to return the emitter units.

Already before the transport unit 4 has entirely passed the wheels 13 during its movement through the apparatus, it has come to engage and to actuate a stationary switch device 19 mounted as shown in FIG. 4. First when the transport unit has entirely passed this switch device, the beforementioned electromagnet is caused to release the pawl 17 so that the emitter unit 11 of each frame structure 7 under the actuation of its spring means is returned to its initial position. Just before or at that very moment the emitter units are dee'nergized.

The detailed construction of the emitter units can be varied within wide limits depending on the type of radiation source or sources used therein. The primary source of energy for the emitters may be electrical current, e.g. from an electric supply'network, or suitable fuel, e.g. in agaseous form, the energy contents of which is converted into radiant energy of any suitable wavelength, for example within the infrared range of radiation or of any other spectral composition that is capable of producing a heating of the shrinkable sheet plastic forming the wrapping 6. For the present invention it is irrelevant what kind of radiant energy there is used and how the same is generated. Contrary thereto it is important for the invention that the radiant energy from the emitter units 11 can be directed and concentrated in a satisfactory manner in a certain main direction towards the passing transport unit which has been indicated by the small arrows adjacent the emitter units in FIGS. 14.

As will be clearly understood from the foregoing description and from the drawing figures, the radiant energy from the emitter units 11 in the apparatus described will at the beginning of a shrinking process be directed towards that portion of the shrinkable wrapping 6 which is on the front side of the passing transport unit 3. Thereafter, the wrapping portions covering the longitudinal sides of the transport unit will be irradiated, and finally the radiant energy will be directed towards the rear side of the transport unit, whereby a satisfactory shrinking of all wrapping portions of the transport unit will be assured, if this wrapping is substantially in the form of a sleeve open at its top. If on the other hand the wrapping instead takes the shape of a cap with an upper portion covering the top of the transport unit, which is frequently the case, it may be suitable to supplement the apparatus with an additional emitter unit which is arranged to irradiate said top or upper wrapping portion. In such a case, this third emitter unit may be tumably mounted about a horizontal axis relative to a horizontally extending, gate-like and swingable frame structure similar to one of the vertically extending frame structures 7 described hereinbefore and this in such a manner that the third framevstructure will pass above the transport unit..0n the other hand, if the transport unit has a very small height, it may be sufficient to use only one single overhead arrangement of such a kind for carrying out the entire shrinking process.

Instead of letting the transport units pass through the stationary apparatus, the latter may, of course, be moved along a predetermined path in relation to a stationary transport unit. The path of relative movement does not necessarily need to be rectilinear or horizontal but may, for instance, be curved and/or vertical. Also other modifications of the apparatus shown and described are feasible within the scope of the following claims.

An apparatus substantially as shown and described hereinbefore and operating with an input power to the emitter units of 10 kW pro meter emitter length (vertically) has in practical testsbeen found capable of accomplishing effective and satisfactory shrinking at a speed of movement of the belt conveyor of 6 meters pro minut, which is, in fact, a rather surprising capacity and gives an idea of the rather small losses therein. Of course, a reduction of the belt speed makes possible a reduction also of the input power.

If it is desirable to still further improve the'shrinking of the wrapping portions at the ends of the transport unit, i.e. at the front and rear sides thereof, this may be achieved by momentarily interrupting the advancing movement of the transport unit at the one hand at that moment, when the forward end of the transport unit just engages the wheels 13, and on the other hand at the moment, when the transport unit has just passed said wheels, i.e. is in the position shown in dash-and-dot lines in'FlG. 4.

I claim:

1. An apparatus for shrinking a wrapping of heatshrinkable sheet plastic that surrounds a transport unit, comprising at least one directional emitter unit operative to emit radiant energy towards the wrapped transport unit and means for effecting a relative movement between said wrapped unit and the emitter unit in a predetermined direction so as to cause said emitter unit to irradiate successive surface portions of the shrinkable wrapping during successive stages of said relative movement, said emitter unit being turnable about at least one pivot axis that is approximately at right angles to the direction of said relative movement, and means being provided to turn said emitter unit about said axis in response to the change in mutual position occurring between the transport unit and said emitter unit during said relative movement.

2. An apparatus as claimed in claim 1, wherein said emitter unit has an elongate shape, the longitudinal axis of which is at least approximately parallel with said pivot axis.

3. An apparatus as claimed in claim 1, wherein said emitter unit is turnable from a first position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the front side of the transport unit as calculated in the direction of relative movement, via a second position, in which its radiant energy is hitting the wrapping of the transport unit in a direction that is substantially normal to the direction of relative movement, and into a third position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the rear side of the transport unit as calculated in the direction of relative movement, said emitter unit being returnable from said third position to said first position.

4. An apparatus as claimed in claim 1, wherein said emitter unit is turnable against the action of spring means tending to return the same to a predetermined initial position.

5. An apparatus as'claimed in claim 1, wherein said means for turning said emitter unit comprises an actuatingarm connected thereto and projecting into the path of the transport unit in order to be actuated upon by the latter during said relative movement.

6. An apparatus as claimed-in claim 1, wherein said emitter unit is turnable about two spaced but mutually parallel pivot axes.

7. An apparatus as claimed in claim 6, wherein said two pivot axes are spaced in the direction of said relative movement.

8. An apparatus as claimed in claim 6, wherein one of said two spaced pivot axes substantially coincides with a centre axis of the emitter unit.

9. An apparatus as claimed in claim 1, wherein said emitter unit is supported at the free outer margin of a gate-like frame structure that is swingable about a first pivot axis, and wherein said emitter unit is turnable relative to said frame structure about a second pivot axis.

10. An apparatus as claimed in claim 9, wherein said swingable frame structure comprises a wheel that is adapted to be actuated upon by the transport unit during said relative movement in order to thereby change the position of said emitter unit relative to the transport unit by causing said frame structure to swing about said first axis.

11. An apparatus as claimed in claim 1, wherein two turnable emitter units are provided to irradiate each one side of a transport unit passing between them. 7

12. An apparatus as claimed in claim 1, wherein said means for effecting said relative movement comprises a driven conveyor for moving the transport unit relative to said emitter unit along a substantially rectilinear path. 

1. An apparatus for shrinking a wrapping of heat-shrinkable sheet plastic that surrounds a transport unit, comprising at least one directional emitter unit operative to emit radiant energy towards the wrapped transport unit and means for effecting a relative movement between said wrapped unit and the emitter unit in a predetermined direction so as to cause said emitter unit to irradiate successive surface portions of the shrinkable wrapping during successive stages of said relative movement, said emitter unit being turnable about at least one pivot axis that is approximately at right angles to the direction of said relative movement, and means being provided to turn said emitter unit about said axis in response to the change in mutual position occurring between the transport unit and said emitter unit during said relative movement.
 2. An apparatus as claimed in claim 1, wherein said emitter unit has an elongate shape, the longitudinal axis of which is at least approximately parallel with said pivot axis.
 3. An apparatus as claimed in claim 1, wherein said emitter unit is turnable from a first position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the front side of the transport unit as calculated in the direction of relative movement, via a second position, in which its radiant energy is hitting the wrapping of the transport unit in a direction that is substantially normal to the direction of relative movement, and into a third position, in which its radiant energy for its main part is hitting that portion of the wrapping which is on the rear side of the transport unit as calculated in the direction of relative movement, said emitter unit being returnable from said third position to said first position.
 4. An apparatus as claimed in claim 1, wherein said emitter unit is turnable against the action of spring means tending to return the same to a predetermined initial position.
 5. An apparatus as claimed in claim 1, wherein said means for turning said emitter unit comprises an actuating arm connected thereto and projecting into the path of the transport unit in order to be actuated upon by the latter during said relative movement.
 6. An apparatus as claimed in claim 1, wherein said emitter unit is turnable about two spaced but mutually parallel pivot axes.
 7. An apparatus as claimed in claim 6, wherein said two pivot axes are spaced in the direction of said relative movement.
 8. An apparatus as claimed in claim 6, wherein one of said two spaced pivot axes substantially coincides with a centre axis of the emitter unit.
 9. An apparatus as claimed in claim 1, wherein said emitter unit is supported at the free outer margin of a gate-like frame structure that is swingable about a First pivot axis, and wherein said emitter unit is turnable relative to said frame structure about a second pivot axis.
 10. An apparatus as claimed in claim 9, wherein said swingable frame structure comprises a wheel that is adapted to be actuated upon by the transport unit during said relative movement in order to thereby change the position of said emitter unit relative to the transport unit by causing said frame structure to swing about said first axis.
 11. An apparatus as claimed in claim 1, wherein two turnable emitter units are provided to irradiate each one side of a transport unit passing between them.
 12. An apparatus as claimed in claim 1, wherein said means for effecting said relative movement comprises a driven conveyor for moving the transport unit relative to said emitter unit along a substantially rectilinear path. 